Bog Hoverfly

Fast Facts

Latin name: Eristalis cryptarum

Notable feature: Red triangular spots either side of its thorax

Conservation Status: Least Concern

Where in the UK: A handful of sites on Dartmoor, South Devon

Bog Hoverfly (Eristalis cryptarum) Male © Steven Falk


The Bog Hoverfly (Eristalis cryptarum) is a small, stout hoverfly that measures approximately 10mm in length.  It looks very similar to a small solitary bee, particularly when it’s flying, having narrow yellow bands on a dark body (thorax) and orange-red legs.  It has two red triangular spots on either side of it’s thorax, which are furry in appearance.

Known as the Bog Hoverfly or Bog-dwelling Drone Fly, it is primarily a bog specialist, but may occur in other wetland habitats.

It was once found throughout all south-western counties in the UK, as far east as the New Forest in Hampshire.  Since the middle of the 20th century the Bog Hoverfly’s range has contracted, for unknown reasons, and it is only now found at a few sites on Dartmoor, Devon.  In some places in Europe, such as Denmark, it is considered critically endangered, or extinct.

The Bog Hoverfly is elusive and easily disturbed, making it a tricky little critter to see.

    • Size: 10mm in length
    • Life span:  Likely an annual life cycle; hoverflies in general can live a few days to a few weeks
    • Diet: The Bog Hoverfly feeds on nectar and pollen and can be found feeding on flowering species such as Devil’s-bit Scabious, Bog Pimpernel, Bog Asphodel and Marsh St John’s Wort
    • Reproduction: Little is known of the larvae and adult ecology of this hoverfly but it is known to require bog/wetland habitat to complete its lifecycle.  It is widely assumed by experts that the larvae of the Bog Hoverfly would be very similar to other Eristalis species but to date Bog Hoverfly larvae haven’t been found to confirm this!
    • When to see:  Adults are generally seen from May to September.
    • Population Trend:  Unknown globally.  Reported as extremely rare in the UK (confined to a handful of sites and listed as a priority species for conservation action) having declined dramatically.  Now considered extinct in Ireland.  European populations also noted to be widely but sparingly distributed and to have declined.
    • Threats: Loss of habitat, in particular loss of wetland/bog/peatland sites as a result of destruction and degradation through human activity.
    • Fun Fact:  To date (2021) Bog Hoverfly larvae haven’t been discovered so there are big holes in our knowledge about this species

The Bog Hoverfly has been identified as a Criteria A and Criteria B species through our Important Invertebrate Area (IIA) work.

How you can help: 

Buglife is working to increase awareness of invertebrates and the Bog Hoverfly through specific projects, including our current Falkirk Lowland raised Bog Restoration Project and previous Slamannan Bog Restoration, Saving Auchenines Mossand our 2012 Bog Hoverfly project survey work but we need your help!

If you would like to volunteer for our current project please get in touch with our Peatland Conservation Officer Melissa Shaw.  There are volunteering opportunities ranging from practical workdays to take out scrub and trees on the bogs, to survey work across the bogs for wildlife and to monitor water levels both before and after restoration work has been carried out.

Find out about our peat bogs and what you can do to help this species by going #PeatFree; check out our blog “Don’t get bogged down with peat…

Join a recording scheme and log your finds – send any records/sightings to the Hoverfly Recording Scheme or download the iRecord app and get recording!

Do remember that we rely on donations to continue our work.  If you have searched, found and learnt about our incredible invertebrates on our website, please do consider Making a Donation, Becoming a Member or maybe even making a purchase in our shop.  For more ideas on how to support our work find out how to Get Involved.  Thank you 🕷